阅读说明：本技术 一种磷钨酸插层类水滑石轻质泡沫隔热材料及其制备方法 (Phosphotungstic acid intercalated hydrotalcite-like light foam heat insulation material and preparation method thereof ) 是由 胡云楚 黄自知 袁利萍 吴袁泊 汤连东 王琼 王文磊 文瑞芝 袁光明 吴义强 胡 于 2019-09-05 设计创作，主要内容包括：本发明公开了一种磷钨酸插层类水滑石轻质泡沫隔热材料及其制备方法,采用共沉淀法制备Zn/Al类水滑石前驱体；采用离子交换法,将磷钨酸盐溶液滴入Zn/Al类水滑石前驱体浆液中,对Zn/Al类水滑石前驱体进行改性制得磷钨酸-Zn/Al类水滑石；将磷钨酸-Zn/Al类水滑石、纳米纤维素、粘接剂混合,经冷冻干燥得到磷钨酸插层类水滑石轻质泡沫隔热材料。杂多磷钨酸插层改性后的ZnAl-LDHs解决了单一ZnAl-LDHs作为阻燃剂时存在的添加量大、阻燃效率低等问题,同时结合纳米纤维素轻质、高杨氏模量、高强度、可再生的特点,赋予泡沫材料低密度、高强度、绿色环保等特点。(The invention discloses a phosphotungstic acid intercalated hydrotalcite-like light foam heat-insulating material and a preparation method thereof, wherein a Zn/Al hydrotalcite-like precursor is prepared by adopting a coprecipitation method; dropping a phosphotungstate solution into the Zn/Al hydrotalcite-like precursor slurry by adopting an ion exchange method, and modifying the Zn/Al hydrotalcite-like precursor to prepare phosphotungstic acid-Zn/Al hydrotalcite-like; mixing phosphotungstic acid-Zn/Al hydrotalcite-like compound, nano-cellulose and an adhesive, and freeze-drying to obtain the phosphotungstic acid intercalation hydrotalcite-like light foam heat-insulating material. The ZnAl-LDHs modified by heteropolyphosphotungstic acid intercalation solves the problems of large addition amount, low flame-retardant efficiency and the like when single ZnAl-LDHs is used as a flame retardant, and simultaneously combines the characteristics of light weight, high Young modulus, high strength and reproducibility of nano-cellulose to endow the foam material with the characteristics of low density, high strength, green environmental protection and the like.)

1. A preparation method of a phosphotungstic acid intercalated hydrotalcite-like light foam heat insulation material is characterized by comprising the following steps:

(1) preparing a Zn/Al hydrotalcite precursor by adopting a coprecipitation method;

(2) dropping a phosphotungstate solution into the Zn/Al hydrotalcite-like precursor slurry obtained in the step (1) by adopting an ion exchange method, and modifying the Zn/Al hydrotalcite-like precursor to obtain phosphotungstic acid-Zn/Al hydrotalcite-like compound;

(3) and (3) mixing the phosphotungstic acid-Zn/Al hydrotalcite-like compound obtained in the step (2), nano-cellulose and an adhesive, and freeze-drying to obtain the phosphotungstic acid intercalation hydrotalcite-like light foam heat-insulating material.

2. The preparation method of the phosphotungstic acid intercalated hydrotalcite-like light foam heat-insulating material according to claim 1, wherein the coprecipitation method in the step (1) is to prepare a mixed salt solution from zinc salt and aluminum salt, and react under the conditions that the pH value is 6-9 and the temperature is 50-90 ℃ to obtain the Zn/Al hydrotalcite-like precursor.

3. The preparation method of the phosphotungstic acid intercalated hydrotalcite-like light foam heat insulation material according to claim 2, wherein the zinc salt and the aluminum salt in the step (1) are prepared according to the molar ratio of zinc ions to aluminum ions of 2:1-3: 1.

4. The preparation method of the phosphotungstic acid intercalated hydrotalcite-like light foam heat-insulating material according to any one of claims 1 to 3, characterized in that the ion exchange method in the step (2) is to drop a phosphotungstate solution into the Zn/Al hydrotalcite-like precursor slurry in the step (1) and react at the temperature of 50-90 ℃ to obtain the phosphotungstic acid-Zn/Al hydrotalcite-like.

5. The preparation method of the phosphotungstic acid intercalated hydrotalcite-like light foam heat-insulating material according to claim 4, wherein the mass ratio of the host Zn/Al hydrotalcite-like to the guest phosphotungstate in the step (2) is 1:3-3: 1.

6. The preparation method of the phosphotungstic acid intercalated hydrotalcite-like light foam heat insulation material according to any one of claims 1 to 3, wherein the size distribution of the nanocellulose in the step (3) is as follows: the nano-cellulose with the fiber length of 1-100 nm accounts for 25% -60%; the nano-cellulose with the fiber length of 100-1000 nm accounts for 35-50 percent; the nano-cellulose with the fiber length of 1 mu m-10 mm accounts for 10% -15%.

7. The preparation method of the phosphotungstic acid intercalated hydrotalcite-like light foam heat insulation material according to any one of claims 1 to 3, wherein the adhesive in the step (3) is at least one of boric acid, tartaric acid, malic acid or citric acid.

8. The preparation method of the phosphotungstic acid intercalated hydrotalcite-like light foam heat insulation material according to any one of claims 1 to 3, characterized in that the mass ratio of the phosphotungstic acid-Zn/Al hydrotalcite-like material, the nanocellulose and the adhesive in the step (3) is 20-55: 40-80: 1-5.

9. The preparation method of the phosphotungstic acid intercalated hydrotalcite-like light foam heat-insulating material according to any one of claims 1 to 3, characterized in that one or more of small molecular alcohol organic solvents, macromolecular organic substances or flame-retardant auxiliaries are also added in the step (3).

10. A phosphotungstic acid intercalated hydrotalcite-like light foam heat insulation material is characterized by being prepared by the method of any one of claims 1 to 9.

Technical Field

The invention belongs to the field of biomass foam materials, and particularly relates to a hydrotalcite-like light foam heat-insulating material and a preparation method thereof.

Background

With the increasing severity of the environmental pollution problem and the exhaustion of petroleum resources, research and development of biodegradable, resource-rich, recyclable, light, heat-insulating and fireproof heat-insulating materials have become a major problem to be solved urgently in society, and the light, heat-insulating and fireproof heat-insulating materials can effectively reduce energy consumption and improve energy utilization rate, and have been widely developed and applied in the fields of aviation, aerospace, chemical industry, construction, machinery, storage, energy and the like due to the excellent characteristics of the materials. However, light refractory materials have the disadvantages of low strength, poor heat resistance and the like, so at present, researches on light refractory materials at home and abroad are focused on the aspects of increasing the mechanical strength of the materials, improving the refractory temperature and the like, and include researches on addition of auxiliaries, preparation methods and the like, such as addition of nano particles, refractory fibers and the like to reinforce the materials.

Ldhs (layered double hydroxides) are layered hydroxides composed of two or more metal elements, and are called layered double hydroxides, hydrotalcite-like compounds or layered composite metal hydroxides. The material consists of laminates which are parallel to each other and have positive charges, and the interlayer is composed of anions for balancing the positive charges of the laminates and interlayer water molecules. The properties of the LDHs mainly include: the exchangeability of interlayer anions, the adjustable property of the composition and the structure of the laminated plate, the acid-base double property, the structure memory effect, the delaminating and the like. Because the LDHs has a unique layered structure and the composition of the laminates and the interlayer anions have adjustable denaturation, the composition structure and the properties of the material are correspondingly changed by introducing new guest anions into the interlayer, and the novel functional material with different structures is prepared. At present, the main methods for preparing anion intercalation modified LDHs include a coprecipitation method, an ion exchange method, molecular self-assembly, a roasting reduction method, a back-mixing precipitation method and the like.

The LDHs not only have the spatial structure characteristics similar to the molecular sieve, but also can be directly used as the rigid support of the flame-retardant expansion layer. The LDHs is expected to be modified to change the interlayer environment of the hydrotalcite, improve the compatibility between the hydrotalcite and the polymer, increase the interlayer spacing of the LDHs, reduce the density of the LDHs, and realize the low-smoke, halogen-free, non-toxic and environment-friendly flame retardant with light weight, small addition amount and high flame retardant efficiency.

Disclosure of Invention

The invention aims to solve the technical problem of overcoming the defects in the background technology and providing a hydrotalcite-like light foam heat-insulating material and a preparation method thereof so as to improve the heat-insulating and flame-retardant effects.

In order to solve the technical problems, the technical scheme provided by the invention is as follows:

a preparation method of a phosphotungstic acid intercalated hydrotalcite-like light foam heat insulation material comprises the following steps:

(1) preparing a Zn/Al hydrotalcite precursor by adopting a coprecipitation method;

(2) dropping a phosphotungstate solution into the Zn/Al hydrotalcite-like precursor slurry obtained in the step (1) by adopting an ion exchange method, and modifying the Zn/Al hydrotalcite-like precursor to obtain phosphotungstic acid-Zn/Al hydrotalcite-like compound;

(3) and (3) mixing the phosphotungstic acid-Zn/Al hydrotalcite-like compound obtained in the step (2), nano-cellulose and an adhesive, and freeze-drying to obtain the phosphotungstic acid intercalation hydrotalcite-like light foam heat-insulating material.

Further, the coprecipitation method in the step (1) is to prepare a mixed salt solution from zinc salt and aluminum salt, adjust the pH value to 6-9, heat the mixed salt solution to 50-90 ℃, and obtain the Zn/Al hydrotalcite-like precursor through vigorous stirring, crystallization and post-treatment.

Further, the zinc salt and the aluminum salt in the step (1) are prepared according to the molar ratio of zinc ions to aluminum ions of 2:1-3: 1.

Further, the ion exchange method in the step (2) is to drop a phosphotungstate solution into the Zn/Al hydrotalcite-like precursor slurry in the step (1), stir vigorously, heat to 50-90 ℃, and react to obtain the phosphotungstic acid-Zn/Al hydrotalcite-like compound.

Further, in the step (2), the mass ratio of the host Zn/Al hydrotalcite to the guest phosphotungstate is 1:3-3: 1.

Further, the size distribution of the nanocellulose in the step (3) is as follows: the nano-cellulose with the fiber length of 1-100 nm accounts for 25% -60%; the nano-cellulose with the fiber length of 100-1000 nm accounts for 35-50 percent; the nano-cellulose with the fiber length of 1 mu m-10 mm accounts for 10% -15%.

Further, the binder in the step (3) is one or more of boric acid, tartaric acid, malic acid or citric acid.

Further, in the step (3), the mass ratio of the phosphotungstic acid-Zn/Al hydrotalcite, the nano-cellulose and the adhesive is 20-55: 40-80: 1-5.

Further, one or more of a small molecular alcohol organic solvent, a macromolecular organic matter or a flame retardant aid is added in the step (3).

The phosphotungstic acid intercalated hydrotalcite-like light foam heat-insulating material is prepared by the method.

The invention adopts coprecipitation method and ion exchange method to introduce phosphotungstic acid anion into Zn/Al hydrotalcite layered structure to prepare phosphotungstic acid intercalation Zn/Al hydrotalcite, then the phosphotungstic acid intercalation Zn/Al hydrotalcite is evenly mixed with auxiliary agents such as nano-cellulose, adhesive and the like, and the environmental-friendly light foam refractory material is prepared after freeze drying. Compared with the prior art, the invention has the beneficial effects that:

(1) the invention adopts phosphotungstic acid-Zn/Al hydrotalcite and nano-cellulose to prepare the light foam refractory material with three-dimensional network structure, multiple pores, low heat-conducting property and high flame-retardant effect for the first time.

The Zn/Al hydrotalcite-like layer plate contains a large amount of hydroxyl and CO₃ ^2–Amorphous water and crystal water, which evolve H upon heating₂O and CO₂Can dilute oxygen and absorb a large amount of heat, reduce the temperature of a combustion system and have the flame retardant effect; and the LDHs is decomposed at the high temperature of 500-600 ℃ to form a composite metal oxide with porous structure and large specific surface area, so that the LDHs can absorb smoke generated in the combustion process and play a role in smoke suppression. Zn can promote the generation of carbon and inhibit smoke.

Because the interlayer and the interlayer anions are connected through hydrogen bonds, the LDHs interlayer anions have interchangeability, and therefore phosphotungstic acid ions can be used for replacing the interlayer anions to modify the LDHs interlayer anions.

The invention inserts the phosphotungstic acid between layered structures of the hydrotalcite-like compound in an ion exchange mode, and can firmly fix the heteropoly acid on the hydrotalcite-like compound through strong electrostatic acting force between the phosphotungstic acid and layered metal ions of the hydrotalcite-like compound.

The invention utilizes P element with good flame-retardant function and tungsten element with high-efficiency smoke-inhibiting function of phosphotungstic acid molecule [ PW₁₂O₄₀]^3–After being introduced into hydrotalcite-like compound, the heat stability and the flame retardance of the LDHs can be obviously improved. Phosphotungstic acid can catalyze cellulose to be dehydrated into ester and solidified into carbon, can effectively delay the pyrolysis of the material, reduce the release of heat and smoke in the combustion process and enhance the thermal stability of the material. Realizes the effects of less addition, light weight and high efficiency.

According to the invention, the phosphotungstic acid intercalation modified hydrotalcite-like compound is introduced into the nano-cellulose foam material, so that the foam material is endowed with excellent heat insulation and flame retardant effects. The ZnAl-LDHs modified by heteropolyphosphotungstic acid intercalation solves the problems of large addition amount, low flame-retardant efficiency and the like when single ZnAl-LDHs is used as a flame retardant, and simultaneously combines the characteristics of light weight, high Young modulus, high strength and reproducibility of nano-cellulose to endow the foam material with the characteristics of low density, high strength, green environmental protection and the like.

(2) The nano-cellulose with certain length distribution is adopted, so that the quantum size effect of the nano-cellulose can be fully reserved, the reinforcing effect of the nano-cellulose with different lengths can be fully exerted, and the mechanical effect of the light foam material is fully guaranteed.

(3) The light foam material contains a plurality of components such as phosphotungstic acid, hydrotalcite-like compound, adhesive and the like, each component exerts a synergistic flame retardant effect, fully exerts a condensed phase flame retardant mechanism and a gas phase flame retardant mechanism thereof and endows the light foam material with an excellent flame retardant effect.

(4) According to the invention, the generation of pore size is regulated and controlled by adding the organic micromolecular solvent into the foam material, so that the generated pores are regularly arranged and have a layered structure, and the pore size distribution is uniform. The composite of the macromolecular organic matter and the nano-cellulose can form a similar reinforced concrete structure, thereby obviously improving the strength, the processability and the like of the foam material. And a small amount of flame retardant auxiliary agent is added to further improve the flame retardant property of the foam material.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a photograph of a flame of an alcohol burner at 500-600 ℃ for each sample of the lightweight foam heat-insulating material: a) CNF; b) CNF/50% ZnAl-NO₃-LDHs/2％H₃BO₃；c)CNF/50％ZnAl-PW₁₂O₄₀-LDHs/2％H₃BO₃；

FIG. 2 shows CNF/50% ZnAl-PW₁₂O₄₀-LDHs/2％H₃BO₃SEM picture of light foam heat insulation material.

Detailed Description

In order to facilitate understanding of the invention, the invention will be described more fully and in detail with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

The preparation method of the phosphotungstic acid intercalated Zn/Al hydrotalcite-like compound/nano-cellulose light foam material comprises the following steps:

(1) preparing a Zn/Al hydrotalcite precursor by adopting a coprecipitation method;

(2) modifying the Zn/Al hydrotalcite-like precursor in the step (1) by adopting an ion exchange method to prepare phosphotungstic acid-Zn/Al hydrotalcite-like;

(3) and (3) mixing the phosphotungstic acid-Zn/Al hydrotalcite-like compound obtained in the step (2), nano-cellulose, an adhesive and other auxiliary agents, and freeze-drying to obtain the phosphotungstic acid intercalation Zn/Al hydrotalcite-like nano-cellulose light foam material.

In a preferred embodiment, the co-precipitation method is as follows: weighing zinc salt and aluminum salt according to the ion molar ratio of 2:1-3:1 to prepare a mixed salt solution, and adding the mixed salt solution into N₂Under the atmosphere, adjusting the pH value to 6-9 by using sodium hydroxide, uniformly stirring, heating to 50-90 ℃, reacting for 6-20 hours, violently stirring, crystallizing, centrifugally separating, washing to be neutral, drying under normal pressure to obtain a Zn/Al hydrotalcite precursor solid, and preparing Zn/Al hydrotalcite precursor slurry.

Preferably, the zinc salt is one or more of zinc nitrate, zinc chloride and zinc sulfate, and the aluminum salt is one or more of aluminum nitrate, aluminum chloride and aluminum sulfate.

In a preferred embodiment, the ion exchange method comprises: dropwise adding a phosphotungstate solution into the Zn/Al hydrotalcite-like precursor slurry in the step (1), violently stirring, heating to 50-90 ℃, and reacting for 5-20 hours to obtain the intercalation modified phosphotungstic acid-Zn/Al hydrotalcite-like slurry. Preferably, the mass ratio of the host Zn/Al hydrotalcite to the guest phosphotungstate is 1:3-3: 1. The ion exchange method utilizes the exchangeability of LDHs interlayer anions to lead [ PW₁₂O₄₀]^3–And exchanging with anions between LDHs laminates to obtain the target product.

Preferably, in the step (3), the size distribution of the nanocellulose is as follows: the nano cellulose with the fiber length of 1-100 nm accounts for 25-60 percent (wt percent); the nano-cellulose with the fiber length of 100-1000 nm accounts for 35-50 percent; the nano-cellulose with the fiber length of 1 mu m-10 mm accounts for 10% -15%. The nano-cellulose with a certain length distribution can fully retain the quantum size effect of the nano-cellulose, can fully play the reinforcing role of the nano-cellulose with different lengths, and fully ensures the mechanical effect of the light foam material.

Preferably, in the step (3), the binder is one or more of boric acid, tartaric acid, malic acid and citric acid, and the addition of the acid substance can further improve the compatibility between the phosphotungstic acid-Zn/Al hydrotalcite and the nanocellulose. Phosphotungstic acid intercalated Zn/Al hydrotalcite-like compound and nano-cellulose are connected into porous foam with uniform pore diameter and a network structure through chemical bonds or electrostatic interaction. The mass ratio of the phosphotungstic acid-Zn/Al hydrotalcite to the nano-cellulose to the adhesive is 20-55: 40-80: 1-5.

Preferably, in the step (3), the assistant further includes one or more of a small molecular alcohol organic solvent, a macromolecular organic substance, and a flame retardant assistant. Wherein the small molecular organic solvent is one or more of methanol, ethanol and n-butanol; the macromolecular organic matter is one or more of starch, xylan and soybean protein; the flame retardant auxiliary agent is one or more of carbon nano tube and graphene. The organic micromolecule solvent can control the formation process of ice crystals in the freeze drying process, so that the pore diameter of the foam material is regulated and controlled, the generated pores are arranged regularly and are in a layered structure, and the pore size distribution is uniform. The composite of the macromolecular organic matter and the nano-cellulose can form a similar reinforced concrete structure, thereby obviously improving the strength, the processability and the like of the foam material. And a small amount of flame retardant auxiliary agent is added to further improve the flame retardant property of the foam material.

The freeze drying method in the step (3) is characterized in that firstly, the water-containing material is frozen to be below the freezing point, so that water is converted into ice, then the ice is converted into steam under higher vacuum, and the pore structure and the size of the composite material can be effectively maintained by temperature programming control, so that the excellent mechanical property of the foam material is ensured.

Comparative example:

1. according to n (Zn)²⁺)/n(Al³⁺) Weighing Zn (NO) 3:1₃)₂·9H₂O and Al (NO)₃)₃·9H₂O, adjusting the pH value to 7.0, reacting for 12h at 70 ℃, and preparing ZnAl-NO by a coprecipitation method₃-LDHs。

2. According to the dry weight percentage ratio of table 1, ZnAl-NO is added₃Mixing and stirring LDHs slurry and CNF (nano cellulose fiber) uniformly; and dropwise adding a certain amount of H₃BO₃And (3) solution. Horizontally placing the uniformly mixed sample in a freeze dryer, and freezing for 12 hours at-50 ℃; then vacuum drying is carried out. Wherein, the vacuum degree is 4.5pa, and the temperature rise process is divided into five stages: the temperature of the first stage is-5 ℃, and the drying is carried out for 3 hours; the temperature of the second stage is 10 ℃, and the drying is carried out for 5 hours; the temperature of the third stage is 20 ℃, and the drying is carried out for 10 hours; the fourth stage is at 30 ℃ and is dried for 10 hours; the temperature of the fifth stage is 40 ℃, and the drying time is 15 h. To prepare CNF/ZnAl-NO₃-LDHs/H₃BO₃Light foam heat insulation material.

TABLE 1 CNF/ZnAl-NO₃-LDHs/H₃BO₃Composition proportioning table of light foam heat insulation material

3. The obtained product was subjected to a fire resistance test, and the results are shown in table 3.

And (3) testing the fire resistance: the fire resistance of the modified LDHs/nano-cellulose light foam heat insulation material is evaluated by adopting XC-24-K-12 type thermocouples produced by American OMEGA company and an OM-DAQ-USB-2400 type data acquisition recorder. And (3) placing the light foam heat-insulation material on a steel plate, placing a thermocouple on the back of the steel plate, and recording the change curve of the back temperature of the sample along with time.

4. The obtained product was subjected to a combustion performance test, and the obtained results are shown in fig. 1.

And (3) testing the combustion performance: a D7100 type single lens reflex camera produced by Nikon corporation of Japan is adopted to record the combustion process of the modified LDHs/nano-cellulose light foam heat insulation material. And (3) placing the sample in an outer flame of the flame of an alcohol lamp for combustion, and testing the combustion performance of the light foam heat-insulating material.

Testing the heat conduction performance: the heat conductivity of the lightweight foam heat insulation material was evaluated by a Hot Disk TPS 2500S thermal conductivity instrument (output power 20mW in transient mode) manufactured by Hot Disk of Sweden.